Many articles of manufacture require lightweight parts which have high stiffness and low coefficients of thermal expansion. For example, actuator arms in computer disk drives are currently made of low density magnesium which exhibits relatively low stiffness (Young's Modulus) and a relatively high coefficient of thermal expansion. The low stiffness of magnesium increases response time and possibly reduces accuracy when large amplitudes of vibration are experienced during movement of the arm.
During operation of most disk drives, the head carried by the actuator arm is lifted from the disk surface by rotational air flow. If the vibrations caused by air flow are sufficiently large, actuator arms (or heads) with low stiffness may contact the disk and damage its surface.
It is generally understood that actuator arms in computer disk drives are subjected to significant forces which can cause vibration. The energy from these vibrations is dissipated as heat which causes the actuator arm to expand. Another source of heat is that generated by electronic components themselves. Thermal expansion is undesirable because it lowers the accuracy of the disk drive. High coefficients of thermal expansion increase the risk of inaccuracy as the dimensions of the arm vary with temperature.
According to one embodiment of the present invention, actuator arms for disk drives should have mechanical properties which are substantially isotropic. These mechanical properties minimize design problems and insure more predictable (i.e., accurate) results during production and operation.
The aluminum-beryllium alloys described in this specification have high moduli of elasticity, high strength to weight ratios and low coefficients of thermal expansion. These properties are suitable for articles of manufacture that are subjected to vibrations and thermal variations.
Aluminum-beryllium alloys are known in the art. Various aluminum-beryllium alloys and/or processes for production are disclosed in U.S. Pat. Nos. 1,254,987; 1,976,375; 2,244,608; 3,147,110; 3,337,334; 3,456,322; 3,506,438; 3,548,915; 3,548,948; and 3,687,737.
Other patents and publications similarly disclose aluminum-beryllium alloys, methods of production or end-use applications. Japanese patent application 56-146387 (1981) discloses a stack of thin alternating layers of aluminum, titanium, nickel or magnesium and flakes of a reinforcing material (beryllium, mica or glass) to provide a sound attenuating plate. U.S. Pat. No. 3,609,855 discloses aluminum-beryllium and beryllium-titanium composites.
None of these art-recognized alloys are substantially isotropic, nor are they specifically directed toward electro-mechanical memory applications such as disk drive arms or disks.